Design And Electrochemical Properties Of Metal Sulfide Composites

With the development of economy and the progress of human society,the depleted traditional energy can no longer meet the rapidly growing energy demand,such as coal,oil,natural gas and so on.Therefore,various energy storage devices have been widely explored and successfully developed.Compared with energy storage devices such as batteries,supercapacitors have the advantages of fast charging and discharging speed,long cycle life,high power density,good rate performance,energy saving and environmental protection,and low cost.However,due to its low energy density,its practical application is limited.Among them,electrode materials are the core components of supercapacitors,and the development of electrode materials with high specific capacity is of great significance for the realization of high-performance supercapacitors.In this paper,a combination of simple hydrothermal,high-temperature calcination and electrochemical deposition methods are used to prepare multi-level structure metal sulfides and their composite electrode materials.The main research contents are as follows:1.Co₉S₈/Ni Co（OH）₂-Mo O₃（Co₉S₈/Ni Co-Mo）battery-type electrode materials with porous hollow heteronanostructures were synthesized in situ on flexible substrate carbon cloth by a simple hydrothermal method.Ni Co（OH）₂-Mo O₃ was grown on the surface of hollow Co₉S₈ nanowires,providing abundant active sites.At the same time,the hollow structure of Co₉S₈ nanowires is conducive to the penetration of the electrolyte and effectively slows down the volume change caused by the continuous charging and discharging process.The morphology and composition of the material were analyzed by scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray photoelectron spectroscopy（XPS）,diffraction of X-rays（XRD）and other characterization methods,and electrochemical tests were carried out in 2 M KOH electrolyte.The results show that the obtained Co₉S₈/Ni Co-Mo electrode has a current density of at 1 m A·cm^-2,its area specific capacity can be as high as 3.07m A h·cm^-2.The hybrid supercapacitor assembled based on Co₉S₈/Ni Co-Mo electrode and activated carbon achieves an energy density of 37.6 Wh·kg^-1 at a power density of228.7 W·kg^-1,and its capacity retention rate is 87.7%after 10,000 charge-discharge cycles.2.Ultrathin carbon layer modified metal oxide/nickel-cobalt sulfide sandwich electrode（Co₃O₄@C@CoNi₂S₄）was synthesized in situ using flexible carbon cloth as a substrate,mainly by simple hydrothermal,high-temperature calcination and electrochemical electrodeposition method.Among them,the ultrathin carbon layer can act as a"highway"for enhanced electron and ion transport,and the horizontally aligned nanosheet structure prevents the electrode from structural collapse during electrochemical reactions.The morphology and composition of the as-prepared composite electrodes were investigated by XRD,SEM,TEM,XPS and other characterization methods.The electrochemical performance of the Co₃O₄@C@CoNi₂S₄ material was tested in a three-electrode system,and the results showed that the specific capacity was 400.6 m A h·g^-1 at a current density of 1 A·g^-1.The hybrid supercapacitor（HSC）was assembled by the compose electrode and activated carbon electrode.When the power density was 1052.8 W·kg^-1,the energy density was 46.5 Wh·kg^-1,and at the same time,it exhibited a good cycle life.After10,000 cycles charging and discharging cycles,the capacitance retention rate is as high as 95.6%.